Tunable magnetron



J. S. DONAL, JR., ET AL 2,638,563

May 12, 1953 w TUNABLE MAGNETRON Filed July 2, 1947 MQMW/w mm y 1953 J. s. DONAL, JR., ETAL 2,638,563

TUNABLE MAGNETRON Y Filed July 2, 1947 3 Sheets-Sheet 2 mm. 0 9mm (Ittqrneg I y 2, .1953 J. 5. DONAL, JR, ETAL I 2,638,563

TUNABLE MAGNETRON 3 Sheets- Sheet .5

Filed July 2. 1947 Imventors Jams 520v, J. 11 aya 2.5mm X jleeezmeifl Bean N attorney Patented May 12, 1953 "UNITED STATES PATENT OFFICE 2,638,563 TUNABLE MAGNETRON John S. Donal, Jr., Princeton, N. J., Lloyd P. Smith, Ithaca, N. Y., and Barremore B. Brown, Lancaster, Pa., assignors to Radio Corporation of America, acorporation of Delaware 1 Application July 2, 1947, Serial No. 758,692

one of aforesaid blocks is mechanically coupled to a member which is movably mounted within the evacuated envelope of the magnetron and is adjustable in accordance with the change in set-.

ting of an external tuning member suitably coupled thereto.

Further in accordance with the invention, the resonant cavities of .the magnetron may be defined by vanes extending from the anode blocks into overlapping relation with one another; preferably, the overlapping ends of each pair of vanes respectively extending from the opposed anode blocks are complementarily stepped to maintain along flux-leakage path between adjacent cavities for all relative positions to which the blocks may be adjusted. More specifically and preferably, the adjacent vanes of each block have the stepson opposite faces thereof in avoidance of distortion of the current paths in the cavity walls formed in part by'the vanes.

The invention further resides in features of construction, combination and arrangement hereinafter described and claimed.

For more detailed understanding of the invention and for illustration of embodiments thereof, reference is made to the accompanying drawings in which:

Figure 1 is a plan View, in section taken on line ll of Figure 2, of a tunable magnetron;

'Figure2 is a front elevational view taken 'on line 2-2 of Figure I;

Figure 3- is a sectional plan view taken on line 3-3 of Figure 2;

Figure 3A is a front elevational view of one of the anode blocks of Figures 1 to 3;

Figure 4 is a fragmentary perspective view of the anode blocks of Figures 1 to 3;

'Figures 5 and 6 are sectional plan views of modifications of the tuning means shown in Figures 1m 3;

'Figure 7 is a sectional view taken on line 1-1 of Fig. 9 of a magnetron tunable by variation of the orientation of its envelope with respect to its anode structure and field magnet;

Figure 8 is a detail end view taken on line 8-8 of Figure 7;

Figures 9 and 10 are sectional end views taken on line 99 of Figure 7 for different angular positions of the magnetron envelope relativeto its anode structure and magnet; and

Figure 11 is a perspective detail view of parts appearing in Figure 7.

Referring to Figures 1 to 4 as examplary of one form of the invention, the anode ill of magnetron II is formed by tworelatively movable/anode blocks [2, 13 disposed side by side within the evacuated envelope 9 and having alignedcylin-- drical openings. The anode block I2 is fastened to the rods or'bol-ts l4 whereas the block [3 is slidable along them to predetermine or vary the I operating frequency of the magnetron as later herein more .specifically described. Thescavity resonators or slots l5 of the magnetron are sep-' aratedby two sets of anode vanes [6A, IGB,

Figures 3 and 4. The vanes IBA extend radially into the cylindrical opening in block W and vanes [6B extend radially into the similar openingv in block I3. The inner faces of the vanes lfiA," I-GB provide spaced parallel anode elements which form a peripherally discontinuous anode cylinder concentric with respect to the cathode C supported by one or both of the inserts or pole pieces [1,. 18. When, as in copending application, Serial No. 751,730, filed June 2, 1947, by John S. Donal, Carmen L. Cuccia, and Barremore B. Brown and entitled Magnetrons, and now abandoned, a. dual cathode is employed, the secondary emission cathode is preferably mounted in the magnetic insert l8 and the primary emission cathode is maintained in the magnetic insert H. For rea- 1 sons which later appear, this avoids flexing of the heater leads to the primary emission cathode.

As the separation between the anode blocks l2, I3 is increased, the effective length of the anode is increased and in consequence the operating frequencyof the magnetron is decreased; It-is desirable that the vanes IGA, HEB overlap 'to maintain continuity of the side walls of each of the anode cavities IS with increasing separation of the blocks l2, l3 as otherwise the divided halves of the cavity may resonate individually producing undesired frequencies in the spectrum of the cavity. Throughout the range of relative; 13 the vanes [6A of adjustment of blocks I2, block I2 project into the anode cavities of block l3, and conversely, the vanes IBB of block I3 continuously project into the anode cavities of Preferably, as shown in Figure 4, the overlap- ,laping ends of each pair of vanes IGA, lfiBare complementarily stepped or notched not only to maintain the continuity of each cavity l5 which could be effected by overlapping without notching but also to insure that the flux-leakage path between adjacent cavities is long so'effectively to suppress undesired couplings between the different cavities for all relative positions to which the anode blocks may be adjusted. i that the-steps or notches be on opposite facesof th'e It is also desirable, as shown in Figure 4,

adjacent vanes of each block in avoidance of distortion of the path of the currents flowing in each half of each cavity. Otherwise expressed, the cut-away surface of each vane faces the cutaway face of the vane adjacent it in one direction and its uncut surface faces the uncut surface of the vane adjacent to it in the other direction. The current paths are therefore of similar configuration in the opposed radial surfaces of each anode cavity; this would notbe so if, for example, all of vanes I 6A were cut away on the right face and all of vanes 16B were complementarily cut away on the left face. The dissymmetry so introduced in each cavity, and here avoided, would undesirably affect the operating characteristics of the. magnetron.

As thus far described, the constructional tea. tures provide for determination of the operating frequency of a magnetron by adjustment of its anode length whether the adjustment be effected during contruction in predetermination of its operating frequency or whether the adjustment be efiected after construction of the magnetron to. vary its operating frequency without destroying the integrity of its evacuated envelope.

The remainder of the description is for the most part concerned with alternative arrangements for eirecting relative adjustment or the anode blocks 112, H of a turnable magnetron, In themodification shown in Figures, 1 to 4,. a air or externally threaded sleeves 1 9.- which are: re.- tatably mqunted on the. rods m engage threaded openings through the movable anode block 1 3;. The crank arms 210., Figures 1 and 2, extending from the threaded sleeves it are. mechanically coupled to thereciprocable operating member 29 which, maybe fastened to. the closed end of a bellows or 'Sylphon. 22' which forms. a deformable section of the evacuated envelope 9 otthe. magnetron. By application of force ex:-.

ernal-ly applied: to, the closed end or bellows 2-2,

the..- bar 2| may be moved to the left or rightthe envelope. St toefiect. rotation of the sleeves, I19; and so, effect.v linear movement of the: anode block l3; toward or awayfrom the anode bloolc 12;, Axial. movement of the, sleeves i9" is or'eliminated by the thrust. washers or ollate. .4,.

For dju tment ortheb 2 o d ierentposings, correspon i w th. dif nt. operatin free be a q e t r ousina or as me 26:1 precludedlby the thrust collars; 29;, 30: 0.

uive ent magnetron is substantial. For example, a parmagnetron, may be; tuned to a selected frequency within; the range; of from about: 990d;

me acycles to. about 10,100 megacy l si. y p. 1

vidipg, for a, total, variation of spacing; of; the,

order jof 0.950; which can be effected by.: movement w'ell,vwithin= the limits of a. bellows. Z2 suited; o; withstand. mos h ric ess r I9, but may als bloclts thepol iecea I1, I 8 and.the. cathode; to

form=an. sembly,-iastened=a aunit to-theblocks;

vement, of, the tuning shaft tunin i nej fi ded v ad ustment f he SQBQIQUQH: etwee ano el cks! of; h

' the axis of. the envelope. The anode blocks MB 3| which are suitably secured to the stationary anode block l2 and to the base ll of envelope 9. More specifically, each of the rods [4, Figure 3, passes at one end through an insulating washer 32, an insulating sleeve 33 and a. cross-piece 34 and at its other end through the insulating collars or washers 35, 36 and the cross-piece 31. The two cross-pieces 34, 3! respectively carry the pole pieces or magnetic inserts ll, I8 which, as above stated, may support the cathode or cathodes of the tube within the anode blocks [2 and 13. In the drawing, a cathode C, of conventional tubular form, is shown as supported by the insert I 8. The cathode is broken away in some of the figures to show the anode vane structure. Thus, when the bolts It are tightened, all components of the electrode assembly are held fast except for the relative movement of the anode blocks previously described.

In the modification shown in Figure 5, a generally similar electrode assembly may be used and consequently only the diiieren-ces in construction are specifically mentioned. In this modification, instead of the threaded sleeves It, there are cams or eccentrics 38' which bear against the angular movement of threaded sleeves EBA, similar to the sleeves t9 of Figs. 1-3, for adjustment. oi the movable anode block 13' is effected by a worm gear arrangement including. worm wheels 43: attached to the sleeves 19A and worms 44. at-v tached to the operating. shaft MB which. issuitably supported by bearing members- 45' attached to the tube envelope; 9. For efiecting change in. efiective length of the anode ill by a force applied externally of the tube envelope, there may i be utilized a pair of, magnetic members 46, 41-,

one onboth 0t which may; be powerfulpermanent magnets, magnetically coupled to each. other through the extension. 28A. of the evacuated tube housing 9, The member. 45- attached to shaft-21B L within extension ZBAmay, for example, serve-as the.- armature; of magnet 47! external-1yrotatably.

mounted on the envelope extension 28A. By' r0.- tation. ofi theexternal tuning member 43, the effectivelength of. themagnetron anode may be in-- creased or decreased. to obtain. thedesired operating frequency as checked, for example, by. a.

calibrated wave meter of suitable type.

In still another form of the invention shown in Figures 7. to L1,. the anode. length andtherefore the operating frequency: may be adjustedsimplyby varying the position of. the magnetron with respect toritsifield magnet.

At, opposite ends of the cylindrical envelope 5,6 of; the .magnetron, therear-e attachedtwo ilxed cams 5|, 52 similarly oriented with rcspectto and. I353; generally similar to, those previously hereinrdescribed, are --provided-with slots--55. which receive the cams 51' and' 52, the..-engagement.be:

tweenthe s-idesofl the.cams andzthewside wallsof the anode blocks preventing movementof: the

blocks. axially of theenvelope. Th'zblOCkSi [2B and l-SBzare biaseditowarm each; other. and-intoengagement; with the-facesof: the cams-51,. 52:.

by two pairs of springsShorgequivalent:

The blocks I23 and 13B are slidably mounted on a pair of H-shaped frames or supports, each comprising a cross-piece 55 free to rotate about theaxis of cams 52 and a pair of end pieces 51 extending parallel to the axis M-M of the cylindrical anode space. As shown, the crosspieces 51 may be slotted to receive pins 58 extending from the blocks IZB, !3B. The. elongated slots permit the blocks to move bodily toward or from each other but prevent movement of either of them in direction normal to the axis M--M.

The anode blocks and their supports may be rotated as a unit with respect to the tube envelope 50 about the axis of fixed cams 5|, 52 and the anode blocks may move linearly in direction along the axis M--M of the anode space.

Accordingly as the envelope 5!] of the magnetron is rotated about its longitudinal axis, the cams 5|, 52 and springs 54 are effective to change the spacing between the anode blocks I2B, I313 and therefore effective to change the operating frequency of the magnetron by variation of its anode length. The magnetic attraction between the pole pieces H, W and the powerful field magnet 59 prevents rotation of the anode blocks as the envelope is rotatedto different angular positions relative to the field magnet. Therefore, since the cams 5|, 52 are attached to and rotate with the envelope, they are effective during rotation of the envelope to separate the anode blocks or to allow them to move toward one another under influence of the biasing springs 54. In Figure 9, the relative positions of the parts are shown for maximum anode length or lowest frequency; the points of engagement between the anode blocks and the cams are at the maximum cam diameter; Upon rotation of the magnet or the tube about the axis of the tube envelope 5!! through an angle of 90 to the position shown in Figure 10, the internal parts assume the positions there shown with the cams at their minimum diameter engaging the anode blocks, to afford minimum anode length or highest operating frequency.

To minimize any change in the coefiicient of coupling between the magnetron and its load circuit as the magnetron is rotated, it is provided that the position of the coupling loop 6! with respect to the anode cavity of the magnetron shall not change as the tube envelope is rotated. More specifically, the concentric output line 60 whose inner conductor 62 is formed into the coupling loop. 6| lies in the axis of rotation of the envelope. The sleeve 63 which forms an ex tension 'of the outer conductor of line 6!] is free to rotate on that portion of the outer conductor which is fastened to the envelope to serve as a mount for the fixed cam 52. The open ,end of the sleeve 63 is connected to the looped end 6| of the inner conductor 62 which is free to rotate inside of the line 60. The disk 64 or equivalent is attached to the sleeve 63 and projects into slots [i5 of the anode blocks to prevent movement of the sleeve 53 and loop 6| axially of the envelope: rotation of the sleeve and loop with respect to the blocks is prevented by a pin and slot or equivalent connection between at least one of the blocks I2B, I33 and the disk 64 or other element fastened to sleeve 53. Accordingly, as the tube envelope 56 is rotated, the anode assembly and coupling loop remain fixed with respect to the field magnet 59 except for relative rectilinear tuningmovement of the anode blocks I23,

I33 which is under control of cams 5|, 52 and springs 54.

The external portion of the output line #60 may project into a wave guide or a resonant cavity, that portion of its inner conductor 62 which extends beyond the outer conductor, to the left in Figure '7, serving as a probe-or antenna whose position remains effectively fixed notwithstanding rotation of the magnetron for tuning of its operating frequency.

It shall be understood the. invention is not limited to the specific arrangements disclosed and that changes and modifications may be made within the scope of the appended claims.

What is claimed is:

l. A tunable magnetron comprising an evacuated envelope, an anode comprising spaced relatively movable anode blocks within said envelope, a cathode positioned within said anode blocks, and means Within said envelope connecting said blocks independently of said envelope, said means being adjustable for varying the eifective length of said anode by adjustment of the separation between said anode blocks. 7

2. A tunable magnetron comprising an evacuated envelope, an anode comprising spaced relatively movable anode blocks disposed side by side within said envelope, a cathode positioned within said anode blocks, means within said envelope connecting said blocks independently of said envelope, said means being adjustable for varying the separation of said blocks to adjust the effective length of said anode and including a tuning member and means externally of said envelope and coupled to said member for operating the latter. 3. A tunable magnetron comprising an evacuated envelope having adeformable section, an

anode comprising relatively movable anode blocks disposed within said envelope, a cathode positioned within said anode blocks, adjustable mechanical means within said envelope connecting said blocks independently of said envelope, and means for transmitting motion through said deformable section to said mechanical means to vary the effective length of the anode by adjustment of the separation of said anode blocks.

4. A tunable magnetron comprising an evacuated envelope, an anode comprising relatively movable blocks within said envelope, and means for varying the effective length of said anode comprising magnetic members respectively attached to said blocks, and cam structure attached to said envelope and engaging said blocks, the orientation of said envelope with respect to an external magnet which restrains said magnet members from rotation with the'envelope determining the spacing of said anode blocks.

5. .A tunable magnetron comprising an evacuated envelope, an anode comprising relatively movable blocks within said envelope, and magnetic means for varying the effective length of said anode comprising a magnetic member movably mounted within said envelope and mechanically coupled to one of said blocks, and means movably mounted adjacent the exterior of said envelope for producing a magnetic field operable on said magnetic member within said envelope, whereby movement of said field producing means with respect to said envelope will cause movement of said magnetic. member and said one of said blocks and thus vary the spacing of said blocks 6. A tunable magnetron anode comprising a pair of anode blocks mounted parallel-to each other for relative movement, said magnetron anode having a plurality of cavity resonators separated by pairs of vanes respectively extendih'g from the :blocks with the vanes of each .pair in overlapping relation, and means connecting said blocks, aid means being adjustable for unii'orml'y 'gthe spacing between said blocks to adjust the effective length "of the anode and Without disturbance of the symmetry of said resonators.

1 A magnetron anode comprising spaced blocks disposed side by'side and whose 'eife'c'tive length is determined 'by the separation between said blocks, said magnetron anode having a plurality of cavity resonators :separated by pairs of vanes respectively "extending from the blocks with the vanes of :each pair in overlapping relatron.

"8. magnetron anode comprising spaced blocks "disposed side by side and having aligned openings and'whose eiie'ctive length is determined by the di's' ce b'etwe'e'nsaid blocks, said magnetrons-none having: aiplurality of cavity resonators separated by pairs 'of vanes respectively extend ing from the blocks within said openings and havihg complementarity stepped ends in over= lapping -relation to provide a long flux-leakage path between adjacent resonators.

'9. A magnetron "anode comprising two spaced bl'oclts disposed side :by side and having aligned openi gs and whose effective length is determined by the distance between said blocks, said magnetron anode having a plurality of cavity resonators separated by "pairs of vanes respec tive1y extending from the blocks Within said openings and having complementarily stepped ends "in overlapping =-relation, the adjacent vanes or eat-2h block :navmg the steps on opposite faces thereof in avoidance'of distortion of the'current paths on the "resonator surfaces.

10. tun-able magnetron-comprisingsan evacuated:enveiopa an anode comprising spaced blocks disposed within said envelope, said magnetron having fa iplur'ality i'of cavity resonators separated by pairs of va'n'esrespectively extending from the blocks with the vanes of each pair in overlapping relation, and tuning means coupled to at least "one ofsaidblo'cks andoperable from the exteriorof said envelope for varying the spacing between said blo'ckswithin limits for which said overlapping exists to adjust the effective length of said 'ano'de without production of spurious irequencies.

l1. .A-tunablesmagnetron comprising ane'vacuated envelope, an anode comprising spaced blocks disposed within said envelope, said magnetron having a plurality bf cavity resonators separated by pairs of vanes respectively extending :from the "blocks-with the vanes of each pair in overlapping-relation, and tuning means coupled to at least one of said'blocks and operable froin'tl-re exterior "of said-envelope for varying the spacing between sai'd blooks within limits for which said overlappingeiii'sts to adjust the effective length oi "said :ia'n'ode without :production of spurious "frequencies, the overlapping ends of said vanes being compl'ementari-ly stepped to provide 'for all settingsof said tuning meansalo'ng flux-leakage path between adj ace'nt l resonators.

l2. n tunable magnetron comprising an evacuate'd enveiope an anode (comprising spaced blocks disposed within said envelope, said magnetron having a plurality of resonant cavities separated by pairs of -vanes respectively extending from the blocks with=-the vanesof each'pair in overlappin 'g relation, and tuning means coupled to at least one of said blocks and operable from the exterior of said envelope for varying thes'pacing between said blocks within limits for which said overlapping exists to adjust the effective length of "said a'no'de Without production of spurious frequencies, the -over1'apping ends of :said vanes being complement'arily stepped to provide for all settings of said tuning :means along fluxleakage path between adjacent resonators, and the adjacent vanes of each block being stepped on opposite faces in avoidance of distortion -of the current paths on the resonator surfaces.

13. ii tun-able magnetron comprising an evacu- 'ated "envelope, an anode comprising relatively movable blocks within said envelope, and means mcvably mounting said anode blocks within said envelope, :said means being adjustable for varying the separation between said blocks and-including cam structure rigidly attached to said envelope and engaging said blocks and spring means biasing said blocks into engagement with said cam structure, whereby movement 50f said anode :blocl'z's with respect to said envelolpe rand attached cam structure will vary the spacing between said blocks and thus vary the effective length "of said anode.

14. it tunable magnetron comprising :anevacu ated-envelope, an anode comprising spaced relatively movable blocks disposed within said onvelepe, adjustable means within said en'vel'op'e connecting said blocks independently of said envelope, and :means disposed in part externally of said "envelope and 'coupled to said connecting means for adjusting said connecting "means .to adjust the separation of said blocks and the effective length of said-anode.

15 A tunable magnetron according to claim 6 wherein said one of said blocks is movably mounted in said envelope and the other of said blocks is fixed to said envelope.

16. A tunable magnetron comprising anevacuated envelope, an anode comprising spaced relatively movable anode blocks within said-envelope, a plurality of spaced parallel anode elements car-riedby each'block with the anode "elements on-one block overlapping the anode elements on the other block, and meanswithin said envelope connecting said blocks :indepeden'tly oi said'envelope, said means being adjustable for varying the .eifectivel-eng-th of said'anode by adjustment of the separation between said anodeblocks.

17. A tunable magnetron according to claim I6, wherein said anode elements and said block-s form a plurality of cavity resonators.

JOHN 'S. DONAL, JR. LLOYD P. 'SMITH. BARREMORE '3. BROWN.

References Gited in the file of thispaten't STATES PATENTS Number -.Name Date -l BOY OQ'Y Bodde i May 1931 g access oeorge Sept. 8, i942 g liqddfi fi :Litton :Dec. 8, .19t2 2glili'iil22 Morton 6 Oct. 15, 1946 2,424,886 Hansell .July 29 i947 a a-ares Burns .Dec. 9. .1947 ass- 431 Retherford .Dec.30 1947 12,473,567 Brown June '21., 19.49 2,492, l55 'Kan'doian Dec. '27. "1949 2,505,529 Crawford et a1. -Apr. 251 '1950 GES moc'eedingsrofi l. R. E.-, vol-. 35,' lia- 4, April i917. 

